1. Field of the Invention
The present invention relates to a projection apparatus, and more particularly, to a projection apparatus for providing multiple viewing angle images.
2. Descriptions of the Related Art
To obtain more vivid and realistic images, corresponding displaying technologies have been developed in succession over recent years to satisfy the viewers' demands. In contrast to early-stage flat panel displays which mainly focus on the improvement of the resolution and colors, the three-dimensional (3D) display apparatuses that have appeared in recent years aim to provide the viewers with a vivid stereoscopic displaying effect.
The stereoscopic displaying effect is achieved primarily by feeding different viewing angle images of an object to the left and the right eyes respectively. According to the vision characteristics of human eyes, when the left and the right eyes receive two images with the same image contents but different parallaxes simultaneously, a 3D image of the object with a sense of level and depth will be perceived by the viewer.
In practice, 3D images are generally viewed either by use of glasses or by the naked eyes; and the trend of technical developments in recent years has moved to the latter. Furthermore, when being viewed with the naked eyes, the images could be viewed in a time multiplex mode or a spatial multiplex mode. The following description gives a brief introduction of the two types.
FIG. 1 is a schematic view of a conventional projection-type stereoscopic display apparatus 1 adopting the time multiplex mode. As shown, the stereoscopic display apparatus 1 adopting the time multiplex mode comprises a plurality of strip-like light sources 11 disposed adjacent to each other, a Fresnel lens 12 and a liquid crystal display (LCD) panel 13. The strip-like light sources 11 each provide a light beam to the Fresnel lens 12 sequentially. The light beam is imaged by the Fresnel lens 12 onto the corresponding viewing zone. However, because one light source can only provide one viewing angle in the aforesaid stereoscopic image displaying technology adopting the time multiplex mode, the number of viewing angles that can be provided is limited by the number of the stripes of the light source. Consequently, with the limitation of the light sources, the resolution of the projector is hard to improve.
FIG. 2 is a schematic view of another conventional projection-type stereoscopic display apparatus 2 adopting the time multiplex mode. As shown, the display apparatus 2 comprises a light source 21, a polarizer 23, a rotary polygonal mirror 25, a panel 27 and a plurality of optical components 29. The light source 21 generates a light beam that is polarized by the polarizer 23 and then reflected by the rotary polygonal mirror 25 onto the panel 27. With the rotation of the rotary polygonal mirror 25, the light source 21 acts as a scanning line light source on the front end of the optical components 29. Then, the optical components 29 project the images of different viewing angles to different viewing zones according to a time sequence. More specifically, the light source 21 generates a first viewing angle image, a second viewing angle image, a third viewing angle image and a fourth viewing angle image on adjacent viewing zones of the panel 27 in different time sequences. However, this projection-type stereoscopic display apparatus requires use of a rotary polygonal mirror 25 to realize the above said results. In addition, the rotary polygonal mirror 25 mostly functions in a mechanical way, so considerable noises are produced due to the friction. Moreover, with the increasing demand for improved resolution, more viewing angles shall be provided, and thereby, the rotation speed of the rotary polygonal mirror 25 must be increased, which makes the aforesaid shortcoming more prominent.
Accordingly, it is highly desirable in the art to provide a stereoscopic display apparatus with advantages such as a higher light utilization factor, no use of mechanical operating elements, a low cost, a simplified optical arrangement and a high resolution and without the above said shortcomings and problems.